(This is an article I put together in 2014 for the International Snow Science Workshop. It is a little dated, but still applies.)
The influence of human factors in how we make decisions in the winter backcountry can turn a safe, fun day in the mountains into a tragic, life-altering event. When things go wrong, it often boils down to the group not being fully aware of how much risk they were taking. In some cases, there is a lack of avalanche awareness. In most cases, the group has training and experience but fails to make appropriate risk assessment for the conditions. Human factors are responsible for the decisions made.
The Trip Planner & Slope Specific Decision Tool (TPSSDT) helps highlight human factors and weave those factors into decisions that involve backcountry travel in and around avalanche terrain. Acronyms are used to remind us of our priorities when travelling in the backcountry. PEACE is often sought and reminds us of our human factors. Food is always a priority and BLTS (Bacon Lettuce & Tomato Sandwich) is used to recall the elements that determine the Danger Rating. The favourite part of the meal for many people is dessert and we use the acronym ALSO DT (ALSO DesserT) to help us remember the factors that determine the potential consequences of getting in an avalanche on a specific slope.
Most mechanized backcountry ski operations reduce human factor errors by deciding what runs they will ski prior to going out in the field. This is done at the guide’s meeting in the morning. By declaring what runs are closed for the day, prior to heading out, guides are less likely to be influenced by human errors when faced with the terrain in the heat of the moment. Recreationists can also reduce the influence of human factor errors by using the Trip Planner & Slope Specific Decision Tool (TPSSDT). The Trip Planner part of the tool involves matching the Danger Rating (Step 1) with the ATES Terrain Rating (Step 2) to make sure the group is planning a trip to appropriate terrain for that day. The Slope Specific Decision Tool is used to ensure that Slope Specific Consequences (Step 3) are in line with the acceptable risk for that group on that day. Use the Avalanche Canada website to determine the Danger Rating (Step 1). Use Avalanche Canada or local resources to find the ATES Terrain Rating for where you want to go (Step 2). Use prior knowledge of terrain, good interpretation of maps, and observations in the field to determine potential consequences of slope specific terrain (Step 3). For example, if the Danger Rating is Considerable for that day (Step 1), the Trip Planner determines that Simple Terrain is in the Green Zone (normal caution), Challenging Terrain is in the Yellow Zone (extra caution), and Complex Terrain is in the Red Zone (don’t go) (Step 2). On that same day, use the Slope Specific Decision Tool to rule in/rule out Minor Consequence Slopes (Green – normal caution), Moderate Consequence Slopes (Yellow – extra caution), Major Consequence Slopes (Red – don’t go) (Step 3).
HUMAN FACTORS: PEACE
For each letter in the PEACE acronym, consider whether the human factors are mostly positive, neutral, or negative. It’s your judgment call. Think about human factors in advance to help plan the day. Then re-evaluate human factors during day, especially the latter two letters, which represent Communication and Euphoria.
Patience. Winter backcountry travel requires a lot of patience. We have to wait for the snow to fall, wait for certain weather, and when it comes to avalanches, we often wait for better stability before committing ourselves and our friends to terrain that has potentially serious consequences. In some years, the snowpack is weak for most of the season and we wait even longer to go to that special place. Sometimes we get sick of waiting! Is the patience factor influencing the group positively or negatively?
Experience. What is the experience level in the group? When travelling in the Yellow Zone of the TPSSDT, it is necessary to understand and recognize the Avalanche Problems, Weather, Signs of Instability, and Snowpack Structure in order to make safe decisions. Experience with avalanche awareness does not always equal safer travel. Roughly two thirds of avalanche accidents involve people experienced in avalanche awareness (Jamieson et al., 2010). Unfortunately, the mountain does not know if you are an expert or not when it comes to avalanches! Negative human factors may lead experienced winter recreationists to take too much risk.
Attitude. Notice the attitude of group members toward risk. It is unlikely that everyone in the group wants to take the same amount of risk. Age, personality, gender, and mood all influence risk taking behaviour. Did you know that brain chemistry is actually rewarded by taking risk? Mood enhancing hormones are released into the blood stream when we do something risky as part of the body’s normal stress response (Sainani, 2014). This rewards the Limbic part of the brain. Another part of the brain, the Prefrontal Cortex controls inhibition. In youth and young adults, the Prefrontal Cortex is still in the developmental stage. This is part of the reason that those younger age groups take more risk than when older, especially when with friends of similar age. Each person has their own risk tolerance. Women seem to have a higher rate of survival than men in backcountry travel, possibly due to evolutionary factors which cause men to have greater sensation seeking behavior than women. Other factors can also tip the scales in our ability to balance risk versus survival including: ego, overconfidence, and peer pressure.
Communication. Accidents are more likely to occur when group members do not communicate and impromptu decisions are made. Barriers to communication can include: distance between group members, wind, the noise of machines, shyness, intimidation, ego, laziness, etc. These problems can be minimized by using the TPSSDT prior to going into the field and then talking about the TPSSDT throughout the day.
Euphoria and other events. The desire for pleasure can sometimes influence our ability to make rational decisions in the field. Other events can also influence the group as the day rolls on. Are people getting tired? Are decisions getting hastier? Is there one piece of information that is being over emphasized while forgetting more important data (remember BLTS)? Is there a chance that lack of activity is leading to a false reinforcement about stability? Are people letting their guard down, especially as the day rolls on? The rest of the TPSSDT will weave the above human factors into further consideration of hazard and consequences.
DANGER RATING: BLTS (Bacon, Lettuce & Tomato Sandwich) (Low, Moderate, Considerable, High, Extreme)
In most cases, use the avalanche bulletin to determine the danger rating. The bulletin is right most of the time. Occasionally the loading, temperature, and/or signs of instability (the LTS part of the acronym) are significantly different in your specific location from what was forecast in the bulletin, and it may be appropriate to change the danger rating. In that case or when no bulletin is available, the recreationist will need very extensive avalanche experience to come up with their own hazard rating based on LTS and knowledge of the history of the snowpack. Special considerations should be made during Extreme danger. During big avalanche cycles, avalanches can overrun their normal path and take out mature forest. This is a time to give yourself extra wide safety margins, and probably avoid all avalanche terrain .
Bulletin. Is there an avalanche bulletin that covers where you want to go? If so, start with, and likely stick with, the danger rating. Unless the group has the expertise to judge a strong specific regional variance from the danger forecast and/or weather is significantly different from what was forecast, it is best for the group to simply use the bulletin rating to assess danger. The ava- lanche bulletin has other specific information about aspect, elevation, temperature, previous avalanche activity, depth of suspected layers, etc., so take the time to read all of the pertinent information.
Loading. New load causes additional stress to the snowpack. The precipitation amount, the rate of accumulation, and transport (wind), all influence the ability of the snowpack to adjust to the load, and weak layers become more vulnerable to fail. Remember that wind transport can add load to lee areas, even once precipitation has ended. Don’t forget that the weight of skiers, boarders, snow machines, etc. add load to the snowpack as well.
Temperature. Temperature can play a substantive role in destabilizing the snowpack. Utilize caution when the temperature nears or climbs over 0 degrees C. Zero degrees is of course the point where snow changes from solid to liquid state. Solar radiation can also warm the snow temperature to Oo C, even when the air is cold. Be wary of abrupt drops in temperature as well, especially when the drop follows a warm spell. This can have a destabilizing effect on the snowpack, making it more brittle.
Signs of instability & Snowpack Structure. The most significant sign of instability is noting previous slab avalanches that have run over the last 48 hours or so. Other signs of instability include cracking, whumpfs, and knowledgeable interpretation of snowpack stability tests. Note that using snowpack tests to give a green light, while ignoring other information, is a sure-fire way to get into trouble and has led to numerous avalanche fatalities. A comprehensive history of the snow pack structure helps avalanche professionals and advanced recreationists predict what layers are vulnerable within the snowpack. This part of snow science is very challenging and perhaps as much art as it is science.
CONSEQUENCES: ALSO DT (ALSO DesserT) (Minor, Moderate, Major)
There is nothing we can do to change the Danger Rating. Nature decides that! However we CAN choose terrain and how we travel through it. Having a bevy of places you can go which are in non-avalanche terrain and/or terrain which has minor or moderate consequences can keep you happy while you’re waiting for conditions to improve. Solo travel requires extra caution because a slope with a typically minor consequence can turn into a serious accident or fatality without a partner around. Whenever venturing into avalanche terrain, safe travel practices are essential. Consider all of the factors below (ALSO DT) to determine the degree of consequence if the slope were to avalanche. This requires both quantitative and qualitative awareness. Remember that human factors (PEACE) can skew your ability to accurately determine consequences. Minor consequences mean there is very little chance of injury. Moderate consequences involve places where there is a slightly greater chance of injury but very little chance of fatality. Major consequences mean you’re recreating in a place where if it avalanches, there is a higher chance of serious injury or death. Smart recreationists typically avoid major consequence terrain when the avalanche danger is Considerable or higher.
Angle. Almost all fatal avalanches are caused by slopes that are between 30 and 50 degrees. Occasionally, it is possible to trigger an avalanche on a slope that is less than 30 degrees. Over 50 degrees, snow tends to sluff more frequently, and slab avalanches are rare, except in Maritime climates, where snow can build on very steep slopes. Don’t forget that there is potential danger while recreating in low angle terrain if there is avalanche terrain above you. There can also be danger on or below cornices when they become fragile and break.
Length. The length of the slope is a factor when someone gets caught in an avalanche. Typically, the longer the slope, the greater the consequences.
Shape. Shape is important in helping create weak areas in the snowpack that are more prone to initiate avalanches. Convex rolls are a classic example. Shape also increases or decreases the consequences of getting caught in an avalanche. When examining terrain, consider how the shape of the slope and its run out will cause more or less snow to be involved in potential trauma and burial. A classic example of shape leading to worse consequences is a gully feature. A slope with an open fan in the run out zone can allow avalanche debris to spread out, possibly decreasing consequence. Other shape features that can influence risk and consequence include support (concavities), safety of high ground, and the abruptness at which a slope transitions from track to run out zone. When planning a route, up or down, consider the shape of the terrain across its length and its width.
Obstacles. Classic obstacles that increase consequences in an avalanche include trees, rocks, and cliffs. Glaciated features (crevasses and seracs) can also ruin the day. In approximately 25% of all avalanche fatalities in Canada, trauma from obstacles was the primary cause of death (Jamieson et al., 2010). Trees aren’t always bad news. Travel through mature forest can often provide a much safer alternative to open terrain.
Depth. The deeper the slab, the greater the consequences on any given slope. A deep slab release can turn a moderate consequence slope into a major consequence slope. It is, however, difficult to predict the potential depth of a slab. Avalanche Bulletins discuss depths of suspected weak layers in the snowpack. Many Avalanche Bulletins also show a specific icon when there is greater risk of triggering a Persistent Slab or Deep Persistent Slab. Persistent and deep persistent slabs, accounted for 72% of all fatalities in a recent study (Jamieson et al., 2010). The destructive potential and timing of triggering these slab types are difficult to predict. They can fail many days after the recent storm. Density also plays a role. In general, the deeper the slab, the greater the density. Wet avalanches can be exceptionally dangerous because of their high density.
Travel practices. All of the previous letters in the Consequence Acronym (ALSO DT) are dependent on either terrain (Angle, Length, Shape, Obstacles) or the characteristics of the snowpack (Depth). Travel practices are based on human behaviour. It’s important to remember that Human factors (PEACE) play a substantial role in that behaviour. Travel practice, in terms of the terrain we choose and the methods we use to move our group through that terrain, is ultimately the most important part of staying safe from avalanche danger. There are many aspects to travel practice and most fatalities have resulted from ignoring one or more of these standard rules of travel in avalanche terrain which include:
- Consider your line in terms of potential consequences.
- Plan in advance your access AND egress when in avalanche terrain.
- Put in a ski cut where possible, especially when trying to manage slab depths of 50 cm or less.
- Utilize terrain features to your advantage, such as ridges instead of gullies. When possible seek out high ground.
- Be mindful of thin spots in the snowpack, which can trigger avalanches that spread onto the thicker parts of the slope.
- Minimize exposure to one person at a time & stop in safe spots.